Various unsaturated alicyclic derivatives of pent-4-en-1-one are already known in the art. Among them, 1-(3,3-dimethyl-cyclohex-6-en-1-yl)-pent-4-en-1-one is certainly the compound presenting the most outstanding properties. It is characterized by a green, herbaceous odour reminiscent of galbanum oil and its odour strength is rarely encountered in perfumery (see e.g. Swiss Pat. No. 586,551).
DE-OS No. 2,917,450 discloses 1-(3,3-dimethyl-cyclopent-5-en-1-yl)-pent-4-en-1-one whose fragrance, though analogous to that of the above cited cyclohexenyl derivative, possesses a fruity tonality of plum and pear type.
Although the compounds of the invention bear a structural analogy with the above cited prior known derivatives, they possess in comparison with these a very distinct odour character. In actual experience, we have found that compounds (I) can reproduce odorous effects which could not be matched by the analogous cited ingredients.